Bond Order

The bond order (B.O.) in diatomic molecules is half of the difference between the total numbers of the bonding electron ) and antibonding electrons therefore

If bond order is zero, the molecule does not exist.

Molecular orbital configuration of some homonuclear diatomic molecules and ions with their bond order etc, are given here.

1.

Bond energy of and bond length is

2.

Bond energy of and bond length is

3.

Since bond order of helium molecule is zero hence helium does not exist as

4.

The bond energy of molecule is low and its bond length is larger .

5.

Since in this case, again bond order is zero hence beryllium does not exist as . It exists as Be.

6.

The bond energy of molecule is and its bond length is . This molecule is paramagnetic due to the presence of unpaired electrons.

7.

Its bond energy and bond length are found to be and , respectively.

8.

Its bond energy and bond length are and respectively.

This order of enrgy level is followed by H, He, Li, Be, B, C and N. this is due to the mixing of 2s and AOs. This mixing is not possible in the case of oxygen, fluorine etc. because in these case the difference between energies of 2s and AOs is larger. Therefore the order of energy level of oxygen, fluorine etc. molecular orbitals is given below and shown in figure

9.

Its bond energy is and bond length is . Since there are more antibonding electrons than hence it is less stable than . Due to the presence of unpaired electrons it is paramagnetic in nature.

10.

Its bond energy and bond length are respectively. This is also more reactive than due ot more antibonding electrons.

11.

Since in this case bond order is zero hence neon does not exist as . It exists as Ne.